1. Field of the Invention
This invention relates to test probes which make electrical contact with electrical components or circuits and, more specifically, to test probes which make electrical contact with integrated circuit pads.
2. Description of Related Art
Integrated circuit chips are usually tested for viability, in wafer form, before leads are affixed to their pads.
In order to test a chip, it is necessary to make electrical connection with it. This is often done by using a test probe which has a plurality of sharply-pointed wires mounted to a rigid test head. The test probe is then pressed against the integrated circuit chip, causing the sharply-pointed wires to come in contact with the pads on the chip.
This type of test probe, however, suffers from several problems.
One problem is that the integrated circuit chip is occasionally damaged by the pressure which is required to obtain a good electrical connection and the integrated circuit chip pad is often marred with an abrasion mark.
Another problem is that it is difficult to mount the sharply-pointed wires closely together, while still maintaining electrical isolation between them. This limits the degree to which complex and densely populated integrated circuit chips may be tested.
A still further problem is that the point contact is often not able to withstand significant current.
A still further problem is that the impedance of the test probe often does not match the impedance of the cable which is connected to the test probe, thereby adversely affecting the upper limit of the frequency which can be used during the test.